The effect of high intensity interval swimming training on GDNF and Ret gene expression in hippocampal tissue in rats with reserpine induced-Parkinson's disease

Parkinson’s disease is a progressive neurological disorder where loss of dopamine neurons in the substantia nigra and dopamine depletion in the striatum cause characteristic motor and nonmotor symptoms. Glial cell line-derived neurotrophic factor (GDNF) is one of the most important neurotrophins that regenerates dopaminergic neurons by receptor tyrosine kinase Ret in Parkinson's disease. The effect of exercise on these proteins are not well known. The present study was conducted to examine the effect of high intensity swimming training on GDNF and Ret gene expression in hippocampal tissue in rats with Parkinson's disease.

In this experimental study, twenty-one male Wistar rats (age 8 to 10 weeks and weight 200-250 gr) were obtained from the Animal Breeding Center of Islamic Azad University, Shiraz branch and transferred to the animal laboratory of this university. Parkinson's disease induced in fourteen rats by injection of 1 mg/kg reserpine during 5 days and then these rats were divided into Parkinson's disease group or training group randomly. The rats in the training group swam 20 times of 30 seconds with 30 seconds of rest between each time for 6 weeks. Additionally, seven remaining rats were included in the healthy control group without any intervention. GDNF and Ret gene expressions were measured in hippocampus 48h after the last session of training using Real Time-PCR. Data were analyzed using one-way ANOVA test and Bonferoni post hoc using SPSS-22 at the P < 0.05.

Data indicated that GDNF gene expression was reduced after induction of Parkinson's disease and this gene was lower in Parkinson's disease group compare to the healthy control group (p=0.001). For Ret gene expression also our results indicated that this gene was reduced after induction of Parkinson's disease and this gene was lower in Parkinson's disease group compare to the healthy control group (p=0.03). After 6-week of training, GDNF gene expression increases compare to the Parkinson's disease group (p=0.009). For Ret gene expression also our results indicated that this gene expression increases compare to the Parkinson's disease group (p=0.007 respectively); while on significant differences were observed between training group and healthy group (p=0.6 and p=0.9 respectively).

In summary it seems that high-intensity interval swimming training that used in this study improves dopaminergic neuron survival in Parkinson's disease by increasing GDNF as a neurotrophine factor and subsequent signaling, receptor tyrosine kinase Ret. According to limit of information, future studies are needed specially in human cases.